1. Field of the Invention
The present invention relates to an image processing apparatus suitable for a digital copying machine, a facsimile system, a filing system, a personal computer, or the like.
2. Related Background Art
A binary (black and white) dot printer, e.g., a laser beam printer, is known as an image reproducing apparatus. When such a printer is used, a binary processing mode must be switched in accordance with an image type (which means an image characteristic or nature) in order to obtain a high-quality reproduction image.
For example, line images, e.g., characters, must be binarized with high precision using a given threshold value, halftone images, e.g., pictures, must be binarized by a dither method in order to reproduce them with high gradation, and dot images must be binarized by a dither method after a scanned image signal has been temporarily smoothed in order to suppress moire noise.
However, when a normal original in which the above-mentioned three types of images are present at the same time is to be binarized, an image type is discriminated while scanning the image, and the processing mode must be switched in real time in accordance with the discrimination result, thus performing binarization.
In realizing such an apparatus, the size of the necessary hardware becomes considerable, and such an apparatus has not been used in practice yet.
In addition, pictures cannot be subjected to accurate image type discrimination, and are often mistaken for line (character) image when they are not
As described above, when a digital image is processed, an apparatus which switches binarizing modes in accordance with an image type (which means an image characteristic or nature) to reproduce a binary image is conventionally known.
When image processing is performed using such an apparatus, two-dimensional smoothing processing of an image is often performed in order to suppress moire with respect to dot images.
When an image type is discriminated, almost all the processing requires such two-dimensional smoothing processing.
Therefore, a processing circuit of this type requires a memory for storing a plurality of lines of an image, and the entire apparatus becomes complex and expensive. As a result, an inexpensive apparatus cannot incorporate such a means.